To use the leader MPM, add
--with-mpm=leader to the configure
script's arguments when building the httpd.

This MPM depends on APR's atomic compare-and-swap operations for
thread synchronization. If you are compiling for an x86 target
and you don't need to support 386s, or you are compiling for a
SPARC and you don't need to run on pre-UltraSPARC chips, add
--enable-nonportable-atomics=yes to the
configure script's arguments. This will cause
APR to implement atomic operations
using efficient opcodes not available in older CPUs.